一、RubyGems
RubyGems是什么
RubyGems简称gem，是一个对Ruby组建进行打包的Ruby打包系统。
gem怎么升级（更新）
sudo gem update --system
Mac OSX 10.11之后会报错，用下面命令：
sudo gem update -n /usr/local/bin —system
二、CocoaPods
CocoaPods是什么
http://www.jianshu.com/p/b64b4fd08d3c
三、安装CocoaPods
安装
1、更新gem
2、查看Ruby的源
gem source -l
终端中：
https://gems.ruby-china.org/
https://ruby.taobao.org/
如果有淘宝的源，需要删除，因为taobao Gems源已停止维护，现由 ruby-china 提供镜像服务。
gem sources --remove https://ruby.taobao.org/
4、设置ruby-china为Ruby的源
gem sources -a https://gems.ruby-china.org/
5、安装CocoaPods
sudo gem install -n /usr/local/bin cocoapods
pod setup
Mac OSX 10.11之前，用下面命令：
sudo gem install cocoapods
报错处理
如果报错
ERROR: SSL verification error at depth 2: self signed certificate in certificate chain (19)
ERROR: Root certificate is not trusted (/C=US/O=GeoTrust Inc./CN=GeoTrust Global CA)
ERROR: SSL verification error at depth 2: self signed certificate in certificate chain (19)
ERROR: Root certificate is not trusted (/C=US/O=GeoTrust Inc./CN=GeoTrust Global CA)
ERROR: While executing gem ... (OpenSSL::SSL::SSLError)
hostname "gems.ruby-china.org" does not match the server certificate
用如下操作：
sudo gem install -n /usr/local/bin cocoapods
pod setup
http://www.jianshu.com/p/39782ea3bb61
http://www.jianshu.com/p/8b61b421dd76
http://www.jianshu.com/p/a94c8a80fb4c
http://www.jianshu.com/p/b5e5cd053464
http://www.jianshu.com/p/b64b4fd08d3c
